1. Field of the Invention
The present invention relates to a silanamine derivative, particularly a silanamine derivative usable as a material for an organic electroluminescence device and a photoconductive drum for electrophotography, and a process for the production thereof. The present invention also relates to an organic electroluminescence device using the above silanamine derivative.
2. Description of Prior Art
Silanamine derivatives typified by N,N'-ditrimethylsilyluric acid, N-trimethylsilylimidazole and trimethylsilyldiethylamine are compounds having Si-N bonds, and these compounds are conventionally used as silylating reagents.
U.S. Pat. No. 4,950,950 discloses cyclodisilazanes usable as materials for forming a hole-conducting layer constituting an organic electroluminescence device (to be referred to as "EL device" hereinafter).
Meanwhile, as other compounds preferred as materials for forming a hole-conducting layer, there are known aromatic tertiary amines (including monoamines, diamines and triamines, to be sometimes referred to as "amino compounds" , see JP-A-63-295695 for example). The ionization potentials of the above amino compounds are generally lower than those of the above cyclodisilazanes. For example, TPD [N,N'-bis-(m-tolyl)-N,N'-diphenyl-1,1'-biphenyl], which is one of the diamino compounds, shows an ionization potential of about 5.5 eV, and hexaphenylcyclodisilazane, which is one of the cyclodisilazanes, shows an ionization potential of about 5.7 eV. Thus, the former shows a lower ionization potential than the latter.
When a hole-conducting layer has a low ionization potential, the actuation voltage of the organic EL device can be decreased. Therefore, the above amino compounds are much more preferred as a material for forming a hole-conducting layer than the above cyclodisilazanes.
Further, a charge-conducting material for forming an electrophotographic photoconductive drum is also required to have a low ionization potential.
However, the amino compounds have the following defects. That is, 4,4'-di-tert -butyl-triphenylamine is difficult to purify, and TPD, when formed into a thin film, undergoes recrystallization with time to deteriorate a service life of the device.